(1) Field of the Invention
The present invention relates to apparatus for mixing liquids. Specifically, the present invention is directed to an aspirator for mixing liquid fertilizers, insecticides and other liquid substances with water.
(2) Description of the Prior Art
Conventional aspirators are generally comprised of a tubular body. The inner diameter of the tubular body converges from the inlet end. The smaller diameter end of this convergent passage is connected to the first end of a second passage section which has a constant inner diameter. This constant diameter passage section either discharges fluid from its second end into the surrounding environment or into a divergent passage section. The result is that the velocity of a pressurized fluid passing through the tubular body is increased through the constant diameter section. As the velocity increases there is a corresponding drop in pressure.
A bore, which is provided in the tubular body, is coupled at a first end to the constant diameter section portion. This bore is also connected, at its other end, with another fluid source; i.e., liquid fertilizer or insecticide. As pressurized fluid, usually water, moves through the tubular body, a low pressure zone is induced within the bore. If the induced low pressure is less than the pressure of the other fluid source, that fluid is drawn through the bore and into the passageway. Thus the two fluids are mixed together and the mixture is discharged from the aspirator.
The typical aspirator is connected at its inlet end to a supply of pressurized water, via a hose for example, and has its discharge end connected to a load, such as a sprinkler or nozzle, by another hose. A major operational problem associated with prior aspirators results from the back pressure induced by the load. As the flow of water through the system is reduced by the load, back pressure builds in the aspirator; especially in the constant diameter portion. This back pressure reduces the velocity and increases the pressure in the constant diameter portion. The result is that the pressure at the discharge end of the bore may equal or exceed the pressure of the second fluid. Should this oxccur, little or no fluid is drawn up through the bore and mixed with the water. Any given aspirator which is inserted between the source of pressurized fluid and a load will cease to function at a predetermined back pressure created in the line by the load. This problem is aggravated when the load is an adjustable flow regulator.
Another problem with conventional aspirators is the lack of ability to regulate the amount of liquid being drawn up through the bore without resorting to small apertures which tend to clog. In conventional aspirators the amount of fluid being drawn up through the bore is a function of the supply pressure of the power stream, i.e., the pressure of the fluid at the inlet to the aspirator, and the amount of back pressure being induced by the load.
A still further problem with conventional aspirators is that they impose a sufficiently large load, in and of themselves, to impede the requisite flow rate when used in conjunction with a mechanically-oscillated lawn sprinkler.